Solvent dewaxing of mineral oils



Patented May 16, 1944 SOLVENT DEWAXING OF MINERAL OILS Luke B. Goodson, Phillips, Tex., James V. Montgomery, Fort Huachuca, Aria, and Robert W. Henry, Bartlesville, kla., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing.

Original application October 28,

1940, Serial No. 363,208. Divided and this application August 10, 1942, Serial No. 454,322

3 Claims.

This invention relates to the dewaxing of mineral oils, and more particularly it relates to dewaxing solvents.

This application is a division of our copending application, Serial No. 363,208, filed October 28, 1940, and nOW issued as U. S. Patent No. 2,303,543, dated Dec. 1, 1942.

It is known that certain organic oxygen containing compounds of the class of aliphatic, cyclic and aromatic alcohols, ethers, and keton-es are antisolvents for paraffin wax at low temperatures and are useful agents for the process of solvent dewaxing.

We have found that certain sulfur containing organic compounds of the general type of the above mentioned oxygen compounds and Wherein the oxygen atom has been replaced by a sulfur atom, such as aliphatic, cyclic, or aromatic thioalcohols, thioethers, thioketones, and 'thioesters are good dewaxing solvents in that they are completely miscible with the waxy oil at elevated temperatures and have a high solubility for the oil component and a low solubility for the wax component at dewaxing temperatures particularly at temperatures of 0 F. and below.

An object of this invention is to provide an improved solvent for use in the dewaxing of mineral oils.

Another object of this invention is to make use of a certain class of sulfur containing organic compounds in the solvent dewaxing of mineral oils.

Still another object of this invention is to provide a dewaxing solvent which may be used in connection with wax antisolvents. v

Still other objects and advantages will be apparent from a study of the disclosure which follows.

These above mentioned types of organic sulfur compounds may be used in a wide range of solvent to oil ratios, depending in some measure upon the particular compound employed and upon the method of separating the wax from the chilled solvent oil solution. We have found that 3 to 1 solvent to oil ratios give good results. These waxy oil solvent solutions may be slow chilled or shock chilled to the required dewaxing temperature. Either method of chilling in the presence of our improved dewaxing solvent gives distinct and sharp edged wax crystals which permit rapid and efiicient filtration. For example, wax precipitated by shock chilling in Carbondale chillers from a 3:1 solvent to oil solution gave a good filter rate. The advantages of shock chilling over slow chilling are readily understood by those skilled in the art.

The application of our invention will give substantially wax free oils having pour points well within the range of effectiveness of pour point depressants such as Paraflow, etc. Furthermore, the use of known wax antisolvents with these compounds gives oils of practically the same pour point as the dewaxing temperature.

The following examples serve to demonstrate the utility of our invention.

Example I One volume of treated waxy Mid-Continent lubricating oil stock of seconds Saybolt Universal viscosity at 210 F. was mixed with three volumes of diamyl sulfide and the mixture heated to F. to insure complete solution. The oil solvent solution was then shock chilled to 0 F. in a Carbondale chiller to precipitate the wax and filtered in the conventional manner. The sulfide solvent was removed from the oil by distillation and gas stripping leaving an oil which had a pour point of 35 F.

Example II One volume of treated waxy Mid-Continent lubricating oil stock of 70 seconds Saybolt Universal viscosity at 210 F. was mixed with three volumes of amyl mercaptan and the whole heated to 150 F. as in Example I. The resulting solution was shock chilled to 0 F. and filtered. The solvent was removed as previously described and the resulting, oil had a pour point of 30 F. f

This invention is not to be limited in any manner by the above given examples which are listed for illustration only. It is to be understood that the homologs of these compounds are closely related in physical and chemical properties and that any of the said homologs which exist in suitable boiling point range as to permit separation from the oil and wax and within suitable melting point range as to remain in the liquid state at dewaxing temperatures, are suitable within degree as dewaxing solvents. Among these monologs and other sulfur bearing compounds which are useful as dewaxing solvents may be listed: normal propyl mercaptan, isopropyl mercaptan, butyl mercaptan, hexyl mercaptan, heptyl mercaptan, cyclo propyl mercaptan, cyclo butyl mercaptan, cyclo amyl mercaptan, cyclo hexyl mercaptan, cyclo heptyl mercaptan, methyl sulfide, ethyl sulfide, methylethyl sulfide, propyl sulfide, butyl sulfide, carbon disulfide, methyl thiocyclo propane, methyl thiocyclo butane, methyl thiocyclo pentane, methyl thiocyclo hexane, methyl thiobenzene, ethyl thiobenzene, mono, di-, and tri-thio phenols, mamma -gemu- 1110 cresols,vetc., or mixtures of the above compounds, such as caustic oils or selected fractions of caustic oils which result from the treating of sour petroleum distillates with caustic, or from acid sludge which results from acid treatment of petroleum distillates containing sulfur compounds. l

These above mentioned compounds "when used with wax antisolvents such as acetone, methylethyl ketone, diethyl ketone, 'dipropyl "keto'ne, dibutyl ketone, and other aliphatic l etones, such as mixed ketone, pyridine, p i colin es, iurifural, aniline, nitrobenzene, etc., give exceptionally good results as dewaxing agents. These sulfur containing compounds in most casesares'ufficiently good oil solvents and have sufficiently low melting points that the addition of a third component, such as toluolin the benzol-acetone process, to lower. the miscibility temperature or to prevent crystallization of thesolv entis unnecessary. This point is .a decidedadvantage since it is much easier to, controla two-component solvent than one containing three components.

The following examples illustrate. the use of solvents composed of mixtures of our organic sufur compounds with wax antisolvents.

Example III III was mixed with three volumes of a solvent composedfoff 70%diamyli sulfide and 30% acetone. Th solution was mixed thoroughly, shock chilled to F. asabove, filtered, and the solvent removed by distillation. The oil resulting from the treatmenthad a'pour point of F.

In carryingjlout our invention, we do not'wi sh to be limited by any special type of dewaxing apparatus, since essentially any standard dewaxing equipment should be satisfactory. For 'dewaxing of the above mentioned Mid-Continent oil stock, the oil to be dewaxed is mixed with the sulfur containing organic compound, as for of filter. wax crystals iormed in our solvent are distinct 10' ,With additionalsolvent mixture at the dewaxing example diamyl sulfide or amyl mercaptan with or without a wax antisolvent, and the mixture warmed gently to insure complete and rapid solution, say to to F. The mixture is then chilled to the dewaxing temperature, say 0 'F., in essentially any type of chilling apparatus available, and filtered in any suitable type Filtration is usually rapid since the and sharp edged. The slack wax may be washed temperature ,to remove the adhering oil solvent solution, while the combined filtrate solution "and washings "comprising dewaxed oil and solvent mixtureare conducted to a solvent oil separat'ing apparatus. This separating apparatus may comprisej a conventional pipe heater and fractionator from which the solvent mixture is removed overhead as vapors and the oil exits from the lower portion thereof and is conducted to storage. The solventv'apors from the above mentioned fractionator are condensed 'andthe condensate conducted to intermediate storage preparatory to reuse. v

v The above given solvent combinations and solvent concentrations may be varied and used in many ways as will be readily understood'by those skilled in the art without departing from theispirit of our invention, and we do'notwi sh to be limited in any manner by the afore' given specific examples.

We claim: 7 I I I 1. The process of dewaxing'mi'neral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising amyl mercaptan and a, wax antisolvent in which the antisolvencis methyl ethyl ketone, chilling' the mixtureof oil and solvent to precipitate thewax, and'removing the precipitated'wax. H

l 2. The process of dewaxing mineraljoilsjjineluding the steps of mixing the waxy oil with a dewaxing solvent comprising approximately amyl. mercaptan by volume and approximately"40% methyl ethylk'etone by voluiii e,

7 chilling the mixture "to precipitate the waxfalnd removing the precipitatedwax. U M

3. The process of dewaxing mineral' o'ilsun- L cluding the steps of mixing the waxy'joil with 'dewa mgsolvent comprising a major proportion, joifamy1 "inerfcaptan and a minor proportion of a wax antisolvent, in which the aiiti'solvent is methyl ethyl ketone, chilling the mixture'to'pre- ,jcjipitate' the wax andsepar'ating the "precipitated wax.

" Lexi; B. oooDsoN.

v; MONTGOMERY. ROBERT HENRY. 

